Seungwoo Paek

Current Status of Pyroprocessing Development at KAERI

Pyroprocessing technology has been actively developed at Korea Atomic Energy Research Institute (KAERI) to meet the necessity of addressing spent fuel management issue. This technology has advantages over aqueous process such as less proliferation risk, treatment of spent fuel with relatively high heat and radioactivity, and compact equipments. This paper describes the pyroprocessing technology development at KAERI from head-end process to waste treatment. The unit process with various scales has been tested to produce the design data associated with scale-up. Pyroprocess integrated inactive demonstration facility (PRIDE) was constructed at KAERI and it began test operation in 2012. The purpose of PRIDE is to test the process regarding unit process performance, remote operation of equipments, integration of unit processes, scale-up of process, process monitoring, argon environment system operation, and safeguards-related activities. The test of PRIDE will be promising for further pyroprocessing technology development.

Performance of the mesh-type liquid cadmium cathode structure for the electrodeposition of uranium from the molten salt

Abstract A mesh-type liquid cadmium cathode (LCC) structure has been devised to improve the performance of the electro-winning process for the recovery of actinides in a molten chloride system. For the verification of its performance, electrodeposition experiments of uranium from the molten LiCl-KCl-UCl3 salt were conducted at 773 K for different current densities using the mesh-type LCC structure. Uranium was successfully collected over 5ߙwt.ߙ% in the LCC without growing uranium dendrites. The mesh-type LCC structure prevented the uncontrolled growth of uranium dendrites into the electrolyte phase above the cadmium surface and caused the LCC deposit to accumulate at the higher in the cadmium phase over uranium solubility in cadmium. After cooling the LCC crucible, its solid deposits were identified as an intermetallic compound UCd11 by EPMA and XRD analysis. The cathode potential profiles from the electrochemical experiments and the chemical structure of the LCC deposits showed that it could be applied practically to recover the actinides above their solubility in cadmium.

Safety Analysis of a Hydrogen Isotopes Process

A nuclear fusion fuel cycle plant is composed of various subsystems such as a hydrogen isotope storage and delivery system, a tokamak exhaust processing system, and a hydrogen isotope separation system. Korea shares in the construction of the International Thermonuclear Experimental Reactor fuel cycle plant with the EU, Japan and US, and is responsible for the development and supply of the storage and delivery system. We thus present details on the hydrogen isotope process safety. The main safety analysis procedure is to use a hazard and operability study. Nine segments were studied how the plant might deviate from its design purpose. We present a detailed description of the process, examine every part of it to determine how deviations from the design intent can occur and decide whether these deviations can give rise to hazards. We determine possible causes and note protective systems, evaluate the consequences of the deviation, and recommend actions to achieve our safety goal.

Adsorption of cobalt(II) ion by titanium-based oxides in high temperature water

Titanium-based adsorbents such as TiO2 and Fe-Ti-O were prepared by hydrolysis of Ti(OC3H7)4 and alkalinizing an equimolar mixed solution of TiCL4 and FeCl2 followed by heat treatment of their hydroxides, respectively. The prepared Fe-Ti-O adsorbent was found to be stable nonstoichiometric ferrous and ferric titanium oxides with pseudobrookite and rutile structures. The Co2+ adsorption characteristics of the adsorbent in high temperature water were investigated in the autoclave.Co2+ adsorption capacity of the Fe-Ti-O adsorbent was determined to be larger man that of TiO2 at high temperatures. The enthalpy changes of 34 and 49 kJ-mol-1 due to the adsorption of Co2+ on the TiO2 and Fe-Ti-O adsorbents indicate that the adsorption is endothermic in the experimental temperature range (15-280 ‡C). From this preliminary study, titanium-based oxides are shown to have good potential applicability for reactor water purification as high temperature adsorption media.

Hydriding Performances and Modeling of a Small-Scale ZrCo Bed

Abstract Korea has been developing nuclear fusion fuel storage and delivery system (SDS) technologies including a basic scientific study on hydrogen storage. To develop nuclear fusion technology, it will be necessary to store and supply hydrogen isotopes needed for Tokamak operation. SDS is used for storing hydrogen isotopes as a metal hydride form. We designed and fabricated a small-scale getter bed of zirconium cobalt (ZrCo). The rapid hydriding of tritium is very important not only for safety reasons but also for the economic design and operation of the SDS. The effect of the initial absorption temperatures on the hydriding of ZrCo was measured and analyzed. The experimental results of the hydrogen pressure of hydriding (ZrCoH2.8) at various cooling temperatures are in agreement with the calculated values using numerical modeling equations. The effect of a helium blanket on hydriding was measured and analyzed. The experimental results of the hydriding with 0 %, 4%, and 8% of helium concentration are in agreement with the calculated values based on numerical modeling equations.

Rapid Cooling Performance Evaluation of a ZrCo bed for a Hydrogen Isotope Storage

Abstract >> The nuclear fuel cycle plant is composed of various subsystems such as a fuel storage and deliverysystem (SDS), a tokamak exhaust processing system, a hydrogen isotope separation system, and a tritium plantanalytical system. Korea is sharing in the construction of the International Thermonuclear Experimental Reactor(ITER) fuel cycle plant with the EU, Japan ,and the US, and is responsible for the development and supply ofthe SDS. Hydrogen isotopes are the main fuel for nuclear fusion reactors. Metal hydrides offer a safe and convenientmethod for hydrogen isotope storage. The storage of hydrogen isotopes is carried out by absorption and desorptionin a metal hydride bed. These reactions require heat removal and supply respectively. Accordingly, the rapid storageand delivery of hydrogen isotopes are enabled by a rapid cooling and heating of the metal hydride bed. In thisstudy, we designed and manufactured a vertical-type hydrogen isotope storage bed, which is used to enhance the cooling performance. We present the experimental details of the cooling performances of the bed using variouscooling parameters. We also present the modeling results to estimate the heat transport phenomena. We comparedthe cooling performance of the bed by testing different cooling modes, such as an isolation mode, a natural convection mode, and an outer jacket helium circulation mode. We found that helium circulation mode is the mosteffective which was confirmed in our model calculations. Thus we can expect a more efficient bed design byemploying a forced helium circulation method for new beds.Key words : Nuclear fusion energy(핵융합), Storage and delivery bed(수소저장용기), Hydrogen isotope(수소동위원소), Metal hydride(금속수소화물), Zirconium cobalt(지르코늄 코발트)

Thermo-mechano-chemical stability of ceramic materials during the electrowinning process using liquid metal electrodes in molten salts

Pyroprocessing, which results in proliferation resistance, shows promise as an alternative to wet processing in the recycling of transuranics. However, the ceramic crucible used in the electrowinning process poses an issue during pyroprocessing. The crucible is chemically unstable and prone to thermal fatigue. In this study, the thermodynamic simulation software HSC (enthalpy, entropy and heat capacity) Chemistry was employed to evaluate the chemical stabilities of different ceramic crucibles containing liquid cadmium as well as liquid bismuth cathodes, which also contained rare earth elements and lithium. The chemical stabilities were experimentally validated by measuring the contact angles between the liquid cathode (LC) materials and four ceramic materials (Al2O3, MgO, Y2O3, and BeO) in situ. The infiltration depths of the liquid bismuth cathode elements were measured using X-ray photoelectron spectroscopy. To determine the Weibull distributions of the investigated ceramics, thermal fatigue tests were performed using plates of the ceramics.

Hydrogen Absorption/Desorption and Heat Transfer Modeling in a Concentric Horizontal ZrCo Bed

Long-term global energy-demand growth is expected to increase driven by strong energy-demand growth from developing countries. Fusion power offers the prospect of an almost inexhaustible source of energy for future generations, even though it also presents so far insurmountable scientific and engineering challenges. One of the challenges is safe handling of hydrogen isotopes. Metal hydrides such as depleted uranium hydride or ZrCo hydride are used as a storage medium for hydrogen isotopes reversibly. The metal hydrides bind with hydrogen very strongly. In this paper, we carried out a modeling and simulation work for absorption/desorption of hydrogen by ZrCo in a horizontal annulus cylinder bed. A comprehensive mathematical description of a metal hydride hydrogen storage vessel was developed. This model was calibrated against experimental data obtained from our experimental system containing ZrCo metal hydride. The model was capable of predicting the performance of the bed for not only both the storage and delivery processes but also heat transfer operations. This model should thus be very useful for the design and development of the next generation of metal hydride hydrogen isotope storage systems.

KOREA'S ACTIVITIES FOR THE DEVELOPMENT OF A DETRITIATION SYSTEM

Tritiated gas and water should be properly treated to minimize an environmental tritium emission in nuclear fusion research facilities. Tritiated gas is usually treated in two steps: it is first oxidized to a tritiated water vapor by a catalyst and then the vapor is adsorbed in a molecular sieve drier. We have used a 1wt.% Pt/SDBC polymer catalyst and Zeolite 13X for the tritiated gas removal system. We confirmed that the decontamination factor of the equipment was more than 100 under a gas flow rate of 90 liters/hr and at a temperature of 65-80 °C.Furthermore we have developed a tritiated organic liquid treatment process. We have used a 0.5wt.% Pd/Al2O3 catalyst to oxidize an organic liquid. The simulated organic liquid was converted to water by over 99%. We have also developed a small scale CECE (Combined Electrolysis and Chemical Exchange) process by combining an LPCE (Liquid phase Catalytic Exchange) catalytic column with SPE (Solid Polymer Electrolyte) electrolysis. The experimental results of the CECE process produced a decontamination factor of 13-20. We used the electrolyte Nafion 117 which was coated with Pt as a cathode catalyst and IrO2 as an anode catalyst. We also tested a palladium alloy membrane for a purification of the hydrogen in the detritiation process.

Development of a 500 kCi BU-type Transport Container

A BU-type container was developed to protect persons, property and the environment from the effects of radiation during the transport of 500 kCi of tritium. Tritium in the form of T2 is immobilized as a solid with a suitable metal to form a solid metal hydride. The container had a cross-linked polyethylene foam in-between a ceramic insulation layer and a polyurethane foam. A prototype shipping package was fabricated and subjected to several tests involving a 9 m free drop test, a 1 m puncture test and a fire test (800°C, 30 min.) in accordance with the Korean regulations. The tritium containment was assured by a helium leakage test not only for a normal condition but also for accident conditions.